That’s today’s lurid National Weather Service map for the Chicago forecast region. Orange means “blizzard warning.” Although Chicago weather cams don’t show anything beyond a typical dreary February day so far, forecasters say the storm is still on track to hit the area this afternoon.

Purple on Lake Michigan means “storm warning.” Here are a couple of details from the statement the Weather Service issued this morning:

* DURING THE STORM WARNING…THE STRONGEST WINDS WILL BE UP TO 50 KT FROM THE NORTHEAST. THE HIGHEST SIGNIFICANT WAVES WILL BE UP TO 18 FT. THERE WILL BE OCCASIONAL WAVES UP TO 27 FT.

Eighteen-foot waves? Twenty-seven-foot waves? Wow. Those are big ones on the ocean. Hard to imagine the mostly placid lake in that condition (though I’ve seen waves big enough to break onto Lake Shore Drive just north of downtown before). Part of the alert the forecasters put out today is a “heavy freezing spray warning.” Here’s what that means:

A HEAVY FREEZING SPRAY WARNING MEANS HEAVY FREEZING SPRAY IS EXPECTED TO RAPIDLY ACCUMULATE ON VESSELS. THESE CONDITIONS CAN BE EXTREMELY HAZARDOUS TO NAVIGATION. IT IS RECOMMENDED THAT MARINERS NOT TRAINED TO OPERATE IN THESE CONDITIONS OR VESSELS NOT PROPERLY EQUIPPED TO DO SO…REMAIN IN PORT OR AVOID THE WARNING AREA.

Since the warning area is the entire lake, probably best to keep your kayaks and ore carriers tied up today.

Update: My friend Pete pointed me to the Chicago Area Forecast Discussion from earlier today that adds this about conditions along the western shoreline of Lake Michigan:

FINALLY…HAVE UPGRADED TO A LAKESHORE FLOOD WARNING FOR ILLINOIS LAKE SHORe COUNTIES. INTENSE NORTHEAST WINDS WILL RESULT IN WAVES BUILDING TO 14-18 FT WITH OCCASIONAL WAVES UP TO 25FT. THIS VERY LARGE WAVES ARE EXPECTED TO BATTER/BEAT/SHRED ANY PANCAKE ICE THAT IS ALONG THE SHORE AND ALLOW THE VERY LARGE WAVES TO RESULT IN COASTAL FLOODING. LAKE WATER LEVELS ARE RUNNING 6-12 INCHES BELOW AVERAGE…HOWEVER WITH 15FT+ WAVES THIS SHOULD BE OF LITTLE CONSEQUENCE. IN ADDITION TO COASTAL FLOODING …THE INTENSE WINDS WILL RESULT IN HEAVY FREEZING SPRAY RIGHT NEAR THE LAKE COATING EVERYTHING WITH A LAYER OF ICE.

Update 2: Here’s a nice piece of forecast geekery–a 30-second animation from the Great Lakes Coastal Forecasting System–of the wind and wave forecast for Lake Michigan for the next five days. If you go by this, maximum wave heights will be generated tomorrow morning and will be about 20 feet in the southwest portion of the lake and between 15 and 20 along the southwestern shoreline.